Walter de Heer, a professor of physics at Georgia Tech in Atlanta who pioneered methods used to work with epitaxial graphene, says the IBM device is a milestone because of its speed and because it was made using practical fabrication techniques. “This is not pie-in-the-sky stuff, this is real,” he says. “This development is really going to turn into a communications device not too long from now.”
“One can apply the same processing technologies to get much closer to a product,” says Avouris. Last year, the same IBM group, and an independent group at HRL Laboratories in Malibu, CA, both made 10 gigahertz graphene transistors using an involved method called mechanical exfoliation. This process involves peeling away layers from a small piece of graphite until a single, atom-thick sheet remains, then setting that down on a substrate and carving it to form a transistor. The problem with this approach is that it compromises graphene’s electrical properties and is not commercially scalable, says Avouris.
The first applications of graphene transistors will likely be as switches and amplifiers in analog military electronics. Indeed, the IBM group’s work is supported in part by the Defense Advanced Research Projects Agency. But the researchers say it will be years before the company begins commercial development on carbon electronics.
De Heer notes that the IBM devices don’t yet realize graphene’s full potential. By carefully controlling the growing conditions, his group has made graphene that conducts electrons 10 times faster than the material used by the IBM team. This higher-quality graphene could, in theory, be used to make transistors that reach terahertz speeds, though de Heer says many things could go wrong during scale-up.
Avouris says the IBM team will work to improve its transistors’ speed by miniaturizing them. The ones it has made so far are 240 nanometers long, which is relatively large–silicon electronic components are down to about 20 nanometers. Avouris also believes that their performance could be improved by making the insulating layer thinner. “The next step is to try and integrate these transistors into a truly operational circuit,” he says.